A control transformer is needed in an electronic circuit that needs constant voltage, or constant current with a lower power, or even volt-amp rating. Generally, it is used together with other filtering devices-such as capacitors-to minimize the differences in the output. Hence, the result will be more constant current or voltage.
A controller transformer is used for industrial applications where electromagnetic devices are also used. Examples of the so called electromagnetic devices include relays and solenoids. With this transformer, it is possible to maximize inrush capability and output voltage regulation, when the electromagnetic devices are energized.
These transformers offer isolation to control components from lighting circuits, and power surges. They also maintain good power regulation under inrush conditions. The inrush current needed for control elements can be 15 times the nominal rating of the transformer. During the active inrush current, the transformer maintains steady as possible the voltage that powers the control element.
These transformers embody high-quality insulating materials, which are crucial to electrically insulate turn to turn windings, primary to secondary windings, layer to layer windings, and ground. A control transformer is vacuum-impregnated with VT polyester resin.
It is also oven-cured to seal the surface and eliminate moisture. It is important to fill the entire unit because it provides a strong mechanical bond. It also offers protection from the environment.
If you need to have proper control transformer specifications, there are three characteristics of a load circuit that you need to determine; besides the minimum voltage needed to operate the circuit.
These three characteristics are the Total Steady-state, Total Inrush, and Inrush Load Power Factor. The Total Steady-state (sealed) VA is volt-amperes that the transformer should deliver to the load circuit for an extended period of time. It is also the amount of current needed to hold the contact within the circuit.
The Total Inrush VA is volt-amperes that the transformer should deliver during initial energizing of the control circuit. The energizing of electromagnetic devices may take 30 to 50 milliseconds. During the inrush period, the electromagnetic controls device may draw normal current several times, which can be between 3 and 10 times.
The Inrush Load Power factor is hard to identify without the detailed vector analysis of all the load components. This analysis, however, is unfeasible. Hence, your safe assumption is 40% power factor. But, there are transformer manufacturers that recommend a power factor of 20%.
It is important that the control transformer matches the load including all electrically energized components in the addressed control circuit, to ensure proper operation. The industrial transformer manufacturers offer selection tables, which are really helpful in determining the appropriate transformer, for the specific application in order for the equipment to be powered correctly.
For more information on control transformer, you can contact the nearest electrical store. They have electricians and electrical engineer who could help you with your needs. You can also browse the web for articles, discussions and tips.
Author Resource:
If you need transformers of various kinds, we have them at http://www.relectric.com/ . These control transformers provide your circuits with the power they need to function properly. Go to Control transformer , to see the specifications of these transformers.
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